One problem related to brake hoses, lines/piping, and fittings has been reported for the 2004 Toyota 4Runner. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Toyota 4Runner based on all problems reported for the 2004 4Runner.
Bought 4th generation 4runner in 1-15 from dealer after owning 4 prior 3rd generation ones and this one is plagued with excessive rust beyond normal wear in frame (some holes), suspension, steering rack and shaft, brake components, virtually everything steel under the body has rusted excessively while body remains rust free. I know 95-03 tacomas and tundras were under frame and brake line recall due to same issue but from the huge number of postings on internet of problem being just as bad if not worse in 3rd and 4th generation 4runner. Yes the frames were a different style but the frames in these 4runners are even worse as problems with rust due to design are eating their way from inside out making it more of a silent killer as it goes unnoticed until rust breaches all the way thru frame and by that point it is not only unsafe to drive, it has been unsafe to drive for a long time before getting to that point. This is major problem as noted in 1000's if not more noted cases on internet forums and Toyota refuses to take responsibility leaving all these people stuck with them and their families and kids that they put in these potential death traps at risk of frame, brake, steering, suspension failures that could result in loss of vehicle control, accidents, and deaths. I've cleaned, sprayed rust preventative oils and paints on areas of concern and rust makes its way back thru in weeks time. The many of owners with this issue are stuck without resources to buy another daily driver and have no choice but to take chance with the uncertainty of potential failure at anytime. Toyota is aware and obviously knew they had rust issue with other model years but they know they have same issues with newer models not included on original frame rust recall and its time they are forced to step up and take responsibility for the faulty frames and underbody steel components.